STATIONARY KINETICS OF ESSENTIAL REACTIONS ON AUTOMOBILE EXHAUST PT-RH AL2O3 CATALYST/

The essential oxidation and reduction reactions over ceria promoted Pt -Rh/Al2O3 catalyst were studied in a laboratory testing system consist ing of a metallic three-way catalyst. Oxidation of CO and propene as w ell as reduction of NO were examined under steady state conditions at 100-400 degrees C and at atmospheric pressure. The concentrations of C O, CO2, total hydrocarbons, NO/NOx and O-2 at the monolith outlet were measured for different gas feeds. The presence of water had a conside rable effect on the kinetics. Water enhanced the oxidation reactions a t low temperatures, while water-gas shift reaction and steam reforming took place at higher temperatures. Steady-state rate equations based on plausible surface reaction mechanisms for the oxidation of CO and p ropene as well as the reduction of NO with CO were derived for dry and wet conditions. The kinetic parameters included in the rate equations were estimated with nonlinear regression analysis. The experimental a nd the predicted concentrations were in good agreement, indicating tha t the kinetic models with their underlying mechanistic assumptions are able to predict the behaviour of the Pt-Rh/Al2O3 catalyst.